Preparation of hydroset textile material



United States Patent 3,128,528 PREPARATION OF HYDROSET TEXTILE BTATERIAL "Bernard Magel, Wilmington, Del., Otto Jack Matray,

from certain graft copolymers.

STATE OF THE ART Textile structures such as'filamcnts prepared from synthetic linear condensation and addition polymers and the fabrics produced therefrom are well known in the textile art, and have shown great utility for many applications. Typical filaments are those spun from polyamides such as polyhexamethylene adipamide, polycaproamide, and the like. These structures are often advantageously set by exposure to hot water, steam or dry heat to improve their resistance to wrinkling. Since such setting treatments are permanent only insofar as the original treating conditions are not subsequently exceeded, it has been the practice to use the most severe treating conditions which the fabric is capable of resisting. Thus, treatment with steam in an autoclave is conventional for stockings which it is desired to make wrinkle-free, as shown, for example, in United States Patent No. 2,157,- 119 to I. B. Miles. Alternatively, broad woven fabrics are conventionally exposed to dry heat in an oven at temperatures of the order of 150-200 C. The practical temperature limit in this latter treatment is imposed by yellowing of the fabric caused by excessive oxidation at these high temperatures. The purpose of these setting treatments is to impart a memory in the filaments whereby they attempt to return to the configuration which they held at the time the treatment was imposed; the return to this configuration is usually accelerated by a plasticizing treatment, such as steaming. Thus, wrinkles introduced during the wearing of garments are more easily removed by steam-ironing.

In contrast to the processes recommended for prior art filaments, it has been discovered that the textile structures of the graft copolymers and polymer mixtures defined herein may be set initially in a predetermined configuration by a relatively low temperature aqueous treatment. While this induced set may be ostensibly removed by a dry heat treatment, for instance by ironing, a memory responsive to a simple aqueous dip will return the filamentary structure to its set configuration. Furthermore, the set, i.e. the original configuration, may be removed and a new configuration may be established without degradation or use of excessively severe thermal treatment. Thus, crepe and stretch yarns may be prepared by the process of this invention and also following its teachings, highly permanent creases or pleats may be set in fabrics.

OBI ECT S OF INVENTION It is an object of this invention to provide a configuration-rctaining textile structure prepared from certain polymeric substrates.

A further object is to impart a durable set to such structures, which may be altered by subjecting said structures to a simple liquid treatment.

Another object is to provide filamentary structures characterized by the property of high wet crease recovery.

Another object is to provide a filamentary structure 3,128,528 Patented Apr. 14, 1964 ice which has a durable set, permanent unless the specified liquid treatment is re-applied, but which may further acquirea temporary set which isreadily impressed, but which is as readily removed by a liquid dip treatment.

A further object is to provide a highly crepeable yarn, and crepe fabrics prepared therefrom.

Another object is to provide a process for making a high stretch yarn.

These and other objects will become apparent in the course of the following specification and claims.

STATEMENT OF INVENTION In accordance with the present invention, a thermally stable predetermined configuration is imparted to a textile structure of a polymer selected from the class consisting of (a) a polymer of a substrate of a carbonaceous polymeric textile modified substantially throughout its crosssectional area, with graft-polymerized side chains derived from an addition-polymerizable monomer selected from the class consisting of an unsaturated organic acid, a Water-soluble salt thereof, an unsaturated organic amide, an unsaturated amine, and an unsaturated alcohol, the said side chains in the homopolymerized non-grafted form being soluble, or at least highly swellable, in water, and (b) a polymer mixture of a synthetic linear fiber-forming polymer and a compatible water-soluble polymer obtained by addition polymerization of an unsaturated monomer of (a) above, by a process comprising the steps of (1) wetting out the said textile structure in the desired predetermined configuration with water at elevated temperature below that at which substantial degradation or melting of the polymer occurs and thereafter (2) setting (by drying or cooling) the said textile while in the said desired configuration. Thereafter the textile will revert to the impressed configuration when wet out with Water in a relaxed condition. The process will be referred to hereinafter as hydrosetting. The above process sets a memory in the structure for the hydroset impressed configuration, which setting is not destroyed on its temporary removal by conventional moderate dry heat treatments such as ironing, heat setting and tensioning.

The textile structure used in the present invention may be a filament or yarn in twisted or untwisted condition. A yarn which is set in the twisted condition and subsequently untwisted, gives an acceptable stretch yarn. Alternatively, a filament may be set in the untwisted condition followed by twisting to yield after weaving a crepe fabric. The textile set may be a fabric, either of knitted or woven construction. The setting may be accomplished while the fabric is held in a flat condition to permit crease removal on subsequent wetting, or predetermined creases or pleats can be impressed upon the fabric. Alternatively, it is obvious that special shapes may also be impressed. The hydroset structure is useful per se, in that it may be used or marketed without further treatment. Thus, the fabric may be sold with permanent pleats or creases impressed therein.

In a preferred embodiment of the present invention, the textile after hydrosetting is subjected to a dry-heat setting to render it adaptable to conventional textile operations. In this step, the structures are temporarily set in. a second configuration, usually to improve ease of subsequent processing. This step is carried out upon the dry hydroset structure while under tension or pressure by using dry heat, either from heated surfaces, or in an oven or the like to temporarily remove the previously hydro set configuration. Thereafter the textile is subjected to conventional operations. For example, a yarn which has been hydroset prior to twisting can be temporarily dry heat set to a much less twist lively condition rendering it more easily knitted or woven. After Weaving the twist liveliness of the yarn is regained when the fabric is wet DEFINITEONS By a graft copolymer is mean the polymer obtained by attaching side chains of polymer species B to the main or backbone chain of a linear, fiber-forming polymer of species A. This type of polymer may be conveniently prepared by forming free radicals on suitable carbon atoms of polymer A in the presence of, or prior to subsequent contact with, a vinyl monomer of species B, whereby vinyl polymerization of B is initiated, and chains of polymer B grow upon the reactive sites of A. The free radicals which initiate grafting of B upon the backbone polymer A are conveniently produced (1) by exposing A to ionizing radiation preferably in the presence of the vinyl monomer B, or (2) by soaking polymer A in monomer B in the presence of a free radical initiator, then initiating vinyl polymerization by heating. Alternatively, the grafting may often be initiated by ultraviolet light, preferably in the presence of a suitable photoinitiator. The structure and preparation of some examples of graft copolymers is discussed in a comprehensive review article by E. H. Immergut and H. Mark in Macromolekulare Chimie 18/19, 322-341 (1956).

For the purpose of the process of this invention, the graft copolymer preferably extends substantially throughout the cross-sectional area of the filaments of the textile structure. When the substrate is man-made this may be attained by forming the graft polymer prior to or simultaneously with filament shaping, or, alternatively, grafting the polymeric side chains directly to the filaments (e.g., as yarn or fabric) under such conditions that the monomer penetrates the filaments before grafting is initiated. Suitable methods of attaining such structures are shownin the examples.

The term carbonaceous polymeric textile is intended to include any filament, fiber, staple, floc, yarn, tow, cord, fabric or the like whether produced from natural, synthetic or man-made materials. In terms of chemical constitution it comprises such textiles formed from a polymer of the class consisting of a synthetic condensation polymer, a synthetic addition polymer, a natural carbonaceous fiber-forming cellulose and protein polymer.

By the term synthetic condensation polymer" is meant a polymer which can be formed by polymerization with elimination of small molecules such as HCl, H O, NaCl, NH and the like as Well as those polymers which on chemical degradation (e.g., by hydrolysis) yield monomeric end products differing in composition from the structural units. Among such polymers may be mentioned polyamides, polyureas, polyurethanes, polyesters, polysulfonamides, and the like and copolymers of such materials. By a synthetic addition polymer is intended a polymer which can be formed by vinyl polymerization, i.e., polymerization which proceeds by combination of an unsaturated monomer with itself or with other unsaturated monomers by linkage at the olefinic bonds. Among suitable monomers for such polymerization may be mentioned styrene, the acrylic esters, vinyl chloride, vinylidene chloride, vinyl acetate, the vinyl ketones, the vinyl ethers, divinyl ether, the halogen, sulfur, nitrogen, and phosphorus containing vinyls, the vinyl silanes, ethylene, propylene, the allyl esters, acrylonitrile, methacrylonitrile, and the like. The concept a natural carbonaceous fiber-forming cellulose and protein polymer comprises those carbonaceous polymers formed in nature which in themselves are fibers or whose derivatives may be manufactured into fiber form. Among such materials is included cotton, flax, jute, silk, wool, fur, hair, wood, regenerated cellulose, cellulose acetate and the like.

The expression polymeric side chains which in homopolymerized non-grafted form are soluble in water provides that the grafted polymeric chains which modify the carbonaceous polymeric textile must be of such nature that when in the non-grafted, i.e., homopolymerized as distinct from copolymerized form, have at least some degree of solubility or high swellability in water. It will be obvious that for use in the hydrosetting process of the present invention the graft copolymer or polymer mixture should not be soluble to any substantial degree in water. In one embodiment useful for the process of the instant invention, the modifying polymer chains are characterized by recurring hydrophilic salt groups. These may be obtained by grafting chains of vinyl polymers which have salt-forming functional groups, such as polyacrylic acid, polystyrene sulfonic acid, polyvinyl pyridine and the like, the said groups being present in the form of a salt which tends to water solubilize the corresponding vinyl polymer. Modifiers particularly useful in producing grafted side chains of polymer B (above) are those npnomers which possess aliphatic unsaturation, and which are polymerizable by free radical mechanism. Although homopolymerizable monomers are preferred, copolyrnerizable monomers may be employed. Suitable ions for salt forming with acrylic acid grafts are alkali metal, ammonium, and amine ions. The polyacrylate salts of these are water-soluble. In contrast, the insoluble calcium poly-acrylate is not soluble and in this sense is not hydrophylic.

The graft copolymer may be formed by grafting the modifier, such as unsaturated acid to the substrate, and, for hydrosetting under moderate conditions, subsequently converting to the salt (either before or simultaneous y with the hydrosetting operation), or alternatively the monomer may be grafted as its preformed salt. Another particularly useful class of monomers is the unsaturated sulfonic acids. The alkali and alkaline earth metal salts, ammonium and amine salts are satisfactory when styrene sulfonic acid has been grafted. Textile structures of the graft copolymers formed by grafting vinyl amines to the substrates defined above, after converting to the amine salt via reaction with strong acids such as sulfuric acid or hydrochloric acid, or after quaternization, e.g. by treatment with alkyl halide, may be hydroset under moderate conditions. Those vinyl monomers capable of readily penetrating the textile substrate are preferred when the grafting reaction is carried out on the filamentary structure. For this purpose, vinyl monomers of low molecular weight (i.e., 8 carbon atoms or less) are most effective. Penetration is assisted by long contact times, higher treating temperatures, and the presence of swelling agents.

Unsaturated amides are also suitable for forming the graft copolymer filaments useful in the process of this invention. It is preferred that said amide be of relatively low molecular weight, to obtain penetration into the filaments. Thus, amides with up to 6 carbon atoms are pre ferred. It is also desirable that the unsaturated amide: be hydrophilic, preferably those forming water-solublehomopolymers. Suitable unsaturated amides are acryl amide, methacrylamide, Nanethylolacrylamide, ethylac-- rylamide, vinylsulfonamides, vinylureas and the like. The preferred classes of compounds are N-alkyl-N-vinyl formamides such as N-methyl-N-vinyl formamide, and espe-- cially N-vinyl lactams (substituted and unsubstituted) such as N-vinyl butyrolactam (e.g., N-vinylpyrrolidone), methyl-substituted N-vinyl butyrolactam and N-vinyl valerolactam.

Alternatively, Where the modifier is of a preformed addition polymer, for which the monomers enumerated above may be employed, and when said polymer is stable at melt-spinning temperatures, it is preferably mixed with 'vention.

I ner.

tion. 'ployed in the examples is a taffeta fabric, woven from the polyamide substrate during polyamidation. For polymeric modifiers which are not sufiiciently melt stable, mixing can take place in solution, and fibers formed by Wet or dry spinning. 'This latter procedure is not preferred, since it will often happen that polymer mixtures prepared in this way may lose the soluble component by extraction from the textile during laundering.

The textile structures to which the process of the instant invention'is applicable include filaments in any form, twisted or untwisted, continuous filaments, tow, staple in any state of processing toyarn, fibrids, textryls and fabrics or pellicles of'knitted, Woven or felted construction.

EXAMPLES The following examples are cited to illustrate the in- They are not intended'to limit it in any man- Because of the commercial importance and wide acceptance of nylon, the preparation'and properties of the product of this invention will be illustrated primarily in terms of polyamide starting materials, which constitute a preferred polymer class for the product of this inven Unless otherwise noted the 66 nylon fabric em- 70 denier polyhexamethylene adipamide continuous filament yarn having a denier per filament of 2.0 (0.22 tex.). The polyamide is produced from hexamethylene diamine and adipic acid (ergo 66), and has a relative viscosity (as defined in United States Patent No. 2,385,890) of 37, 39 equivalents -NH ends and 92 equivalents of -COOH ends per 10 grams of polymer (referred to hereinafter as 39 amine ends and 92 carboxyl ends,

respectively).

Crease recovery is evaluated by crumpling a fabric in 'the hand, and observing the rate at which it recovers from this treatment. Wet crease recovery indicates the rate and extent of disappearance of creases from the crumpled fabric when it is wetted. Numerical values are obtained using the Monsanto crease recovery method, described as the vertical strip crease recovery test in the American Society for Testing Materials Manual as Test No. D1295-53T. In determining wet crease recovery by this method, the specimens are soaked in distilled water Containing 0.5% by weight of Tween 20, a polyoxyalkylene derivative of sorbitan monolaurate, a wetting agent, for at least 16 hours. Immediately prior to testing, excess water is removed from the test fabrics by blotting between layers of a paper towel. Results are reported as percent recovery from a standard crease in 300 seconds.

Example 1 A sample of 66 nylon fabric is soaked in an aqueous solution containing 10% acrylic acid for one hour. While still wet it is irradiated with electrons of 2 million electron volts (mev.) to a dose of l megarad (mrad), a rad being the amount of high energy radiation of any type which results in an energy absorption of 100 ergs per gram of Water or equivalent absorbing material.

The fabric sample is ironed conventionally to make it wrinkle free, then a crease is ironed into it, followed by pouring on the fabric sample a 5% aqueous solution of sodium carbonate to form the salt of the grafted acid. The crease is then pressed'into the wet out fabric with a steam iron. The fabric is then dried in the creased position. The crease appears as though set into the fabric. Thereafter this hydroset crease is ironed out with dry heat so that it is practically invisible. Upon subsequent wetting of the relaxed fabric the crease immediately reappears.

Example 2 A 70 denier (7.8 tex.) 34 filament nylon yarn is grafted with acrylic acid, following the soaking and irradiation procedure of Example 1. The yarn is then knitted into tubing and is boiled in dilute sodium car- Thereafter the dried tubing is unraveled into yarn, the yarn is backwound onto cones and set in the dry condition on the cone 'under the winding tension. On removal from the cone, the yarn-is straight and uncrimped. Upon immersion in water, the yarn snaps into a crimp, and remains crimped on drying. A bulky'and elastic fabric is produced when the yarn is woven and subsequently wetted.

In another process variation, the acid-grafted 70 denier (7.8 tex.) 34 filament yarn, prepared as described above, is twisted 30 turns 2 per inch, and is then boiled in dilute sodium carbonate solution, setting the twist in place while forming the sodium salt. The sample is then dried and twisted in the reverse direction, and wound onto a package. Due to the winding tension, the packaged yarn is substantially straight. HoWe ver when it is removed from the package and immersed in water ahighly crimped yarn is produced.

Example 3 A skein of 12 denier (1.3 tex.) 66 nylon monofilament yarn, is soaked in 30% acrylic acid for 16 hours, centrifuged to remove excess acid, and irradiated 1 mrad with 2 mev. electrons. The skein is hydrosetby boiling in 5% Na CO solution, then is rinsed and dried, after which it is backwound onto a package and twisted 50 turns per inch. The twisted yarn is given a temporary set by heating it while dry on the package for 2 hours at 82 C., in an atmosphere at 65% relative humidity. The yarn is then sufficiently stable so that it is readily knitted into a circular knit stocking. The product has excellent reversible stretch after wetting out.

Example 4 A skein of acrylic acid grafted yarn, prepared as in Example 2 to have 2300 equivalents of carboxyls per 10 grams of polymer, is hydroset as a low twist (1 turn per inch Z) yarn, by boiling in 5% sodium carbonate solution, followed by rising and drying. Half of the yarn is then twisted to 60 turns per inch Z, and half 60 turns 8. The twisted yarn is then twist-set by heating for 30 minutes at 82 C., 65% RH. to make it weavable. The yarn is then woven as filling in a plain Weave fabric. Two picks of Z twist are alternated with two picks S twist. The fabric coming from the loom looks like a normal plain Weave fabric, but when immersed in water, the temporary setting is removed, the filaments attempt to return to their untwisted configuration, and as a result, the fabric shrinks and a crepe is produced.

The crepe is given an acid bleach which, simultaneously with bleaching, converts the sodium acrylate chains to acrylic acid chains, removing the previous solset. The fabric is then soaked in dilute Na CO solution, stretched, and heated at 180 C. for 5 minutes-in steam, stabilizing the crepe by a hydroset in the new configuration.

Example 5 A swatch of 66 nylon fabric is soaked in a solution of 15 ml. of methanol and 15 ml. of 4-vinyl pyridine, at a temperature of 60 to 65 C. for a period of 20 minutes. The swatch, while still wetted with the solution, is enclosed in a polyethylene bag and irradiated with -2 mev. electrons to a dose of 2 mrad. After excess monomer and ungrafted homopolymer are extracted by washing four times in distilled water at C., the weight gain is observed to be 27.0% which corresponds to 2570 equivalents of pyridine per .10 grams of polymer. This sample held in a flat position is then hydroset by heating at the boil for /2 hour in a solution containing 2 drops of concentrated sulfuric acid in ml. of Water. When the sample is dried, and crumpled in the hand it is found that wrinkles so impressed are immediately removed on subsequent immersion in water. When the fabric is converted back to the pyridine form by a treatment with dilute base, creases produced by crumpling the dry fabric are not removed to an appreciable degree by a subsequent immersion in Water. This demonstrates the high crease recovery at moderate hydrosetting temperatures characteristic of the amine salt.

A second portion of the polyvinyl pyridine grafted nylon is hydroset by quaternization, i.e. by heating the fabric sample at reflux in 500 ml. of methanol and 50 grams of butyl bromide for 15 hours. The fabric sample is washed twice in hot methanol and once in water at 80 C. to remove any free butyl bromide. The weight gain after quaternization indicates that approximately 55% of the available pyridine groups have been quaternized. A test of the dried fabric demonstrates the same wrinkle recovery properties previously observed when the polyvinyl pyridine is converted to the sulfuric acid salt.

Example 6 Fabrics are prepared from filaments spun from the polymers listed in Table I.

TABLE I Sample: Polymer 6A Polyamide from meta-xylylene diamine and adipic acid.

613 Polyamide from Z-methyl hexamethylene diamine and oxalic acid.

6C Polyurethane from piperazine and ethylene glycol chloroformate.

6D Polyamide from caprolactam.

Plain weave fabrics made from 34 filament, 70 denier yarns of the polymers identified in Table I are soaked in 20% aqueous acrylic acid solution, room temperature being used for all samples except 6B, which is soaked at 60 C. Following the soaking treatment, the samples are irradiated while still wet, using 2 mev. electrons and a dose of 1 mrad. Following the irradiation procedure, the samples are washed to remove ungrafted acid and the sodium salt modification of each is prepared by heating the fabric at 70 C. for /2 hour in a 1% sodium carbonate solution. After conversion to the sodium acrylate form, each dried sample is crumpled in the hand, then wetted with water to determine the degree to which the wrinkles are removed. It is observed that each of the sodium acrylate-grafted Samples is substantially free from wrinkles after the wetting treatment. When a portion of the original ungrafted fabric from each fiber is given the same treatment the wrinkles remain visible. sodium acrylate grafted samples are boiled in dilute calcium chloride solution, the grafted sodium acrylate is converted to calcium acrylate. A repetition of the crumpling test upon the calcium acrylate derivative shows no solset under the solvation setting conditions employed for this derivative.

Example 7 A series of 66 nylon fabric samples are prepared in form by acetic acid treatment.

[Each of the three samples are divided into two portions, and are then dyed in the dye baths described in Table IV, with the results listed in Table III.

When the p TABLE III D Anthraquinone Green GNN Du Pont Milling Red SWB Initial Color After Washing Initial Color After Washing 7A.-. light dyeing--. decrleased light dyeing little change.

co or.

7B deep dyeing--. d0 deep dyeing Do. 7C do d0 do Do.

Although sample 7C is chemically the same as sample 7A, from the dyeing results it is obvious that important physical changes have been made in the structure of the fibers. It is thought that these changes are the result of an opening of the fiber structure, so that it is more easily penetrable by the dye molecules. The improved wash fastness observed with the Du Pont Milling Red as compared to the Anthraquinone Green is thought to be due to the fact that the red dye has a larger dye molecule and hence does not diffuse from the open structure as readily as the smaller green dye molecule.

When the experiment is repeated, starting with the calcium form of the acid-grafted polyamide and converting it to the sodium form followed by regenerating the calcium form, the regenerated calcium form has improved dyeability over the virgin calcium sample.

Examination of samples 7A and 713 by low angle X- rays indicates that the sodium form apparently contains more or larger voids [within the fibers. Conversion to the calcium salt directly from the acid opens the structure less than conversion to the sodium salt. However, when the calcium salt is prepared via the sodium salt, the open structure is obtained.

The composition of the dye baths used in this experiment is indicated in Table IV. Both dyes are classed as acid dyes.

1 Triton X-lOO is an octyl phenyl polyether alcohol wetting agent. 2 Duponol D is the sodium salt of unsaturated long-chain alcohol sulfate, 2. surface-active agent.

Both dye baths are adjusted to a pH of 4, using potassium acid phthalate buffer. A one-hour immersion is employed with bath No. 1 at to C.; for No. 2, dye at boil for 90 minutes.

The ability of a textile structure to revert to its hydroset configuration upon wetting can be expressed in terms of wet crease recovery which is determined as previously indicated. This property is expressed in terms of wet crease recovery in the following examples.

Example 8 Two swatches of 66 nylon fabric coded 8A and 8B are soaked in different aqueous solutions of acrylic acid for one hour, as indicated in Table V. While still wet with solution, they are irradiated with electrons of 2 million electron volts (mev.) to a dose of 1 megarad (mrad). Following the irradiation excess acrylic acid and ungrafted acrylic acid homopolymer are removed by rinsing in hot distilled Water. Portions of each sample are analyzed to determine the equivalents of grafted acrylic acid with the results also indicated in Table V. Portions of samples in the polyacrylic acid form 8A and 8B are tested for wet crease recovery, the results being listed TABLE V Cone. Wet Crease Recovery, Acrylic G O 011, Percent Sample Acid, 10 gm.

Percent H Na Ca 8A 10 l, 100 68 87 59 8B 25 1,680 72 94 66 1 Equivalents of acid per million grams of nylon.

An unmodified control sample, containing 90 car'boxyl equivalents per million grams of polymer has a wet crease recovery of 70%.

A third swatch of fabric, 80, is prepared to contain 22.2% acrylic acid (2400 equivalents of COOH/ 10 gm); this swatch is hydroset fiat in water in a pressure cooker at 130 C. for 30 minutes. The wet crease recovery of 8C is thereby increased from 75 to 82%.

When the procedure for SA is repeated, using 1 methacrylic acid instead of the acrylic acid, 1190 equivalents of carboxyl groups per 10 grams of polymer are grafted. The Wet crease recovery of the hydroset acid form of grafted polymethacrylic acid is observed to be 64%, whereas the wet crease recovery of the hydroset sodium salt form is 91%.

Example 9 A swatch of acrylic acid-grafted 66 nylon fabric is prepared according to the procedure of sample 8B in Example -8. It is converted to the sodium salt form by boiling dilute sodium carbonate solution. When tested, it is found to have a wet crease recovery of 96%. The sample in the sodium acrylate form is then boiled in dilute calcium acetate solution. The calcium ions preferentially replace the sodium ions in the grafted acrylic acid chains, so that they are present as calcium acrylate grafted to the nylon polymer. The Wet crease recovery drops to 73%. When the calcium ion is removed by boiling in a sodium hexametaphosphate solution, which acts as a calcium ion sequestrant, followed by boiling in dilute sodium carbonate, the original high wet crease recovery of the sodium form: is restored.- When the sample in its sodium form is boiled in dilute acetic acid, converting it to the polyacrylic acid graft, the wet crease recovery again drops to that of unmodified nylon. The original high vwet crease recovery typical of the grafted sodium acrylate is again restored on boiling in dilute sodium carbonate solution.

Example 10 Graft copolyrners wherein acids other than carboxylic are grafted to the nitrogenous condensation polymer substrate are also applicable to the process of this invention as shown by the following example. An especially useful acid is styrene sulfonic acid.

The styrene sulfonic acid used to react with the modified polyamide employed in this example is prepared (by ion exchange) from a commercial sodium styrene sulfonate product. consist of 76 parts of styrene sulfonic acid (SSA) and 24 parts sodium styrene sulfonate (SSS), making 100 parts of monomer. Swatches of nylon fabric are soaked in an aqueous solution of SSA-SSS or" 35% monomer The product is found by analysis to 10 content for about 16 hours at room temperature, followed by irradiation with 2 mev. electrons to a total dose of 1 mrad. After removing homopolymer and washing, a weight gain of 25% is observed, and analysis shows 890 equivalents of acid per 10 grams of fabric (sample 10C, Table VI).

The acid modification is converted to the sodium salt by agitating in 0.5% sodium carbonate solution for 15 minutes at 25 C. The sample is spread out flat and is dried at room temperature. When the dry fabric is crumpled, introducing wrinkles, then wetted, the wrinkles are not removed; this behavior is substantially the same as observed in an unmodified (no grafted acid) control (i.e., sample 10F).

When the sample is boiled for 15 minutes, in a fiat configuration (e.g., held flat between two pieces of screen), and thereafter dried the hydroset is completed. After rinsing and drying, wrinkles introduced by crumpling are immediately removed by wetting. In addition, the sample has a high Wet crease recovery, as indicated in Table VI, sample 10C. The sample is then converted to the calcium salt by boiling for 30 minutes in a 1% calcium acetate solution (100 ml./ gm. fabric). Unlike ny- 1011 with grafted water-insoluble calcium acrylate, which has the same wet crease recovery as unmodified nylon, the calcium salt of styrene sulfonic acid-modified nylon shows a high wet crease recovery equivalent to the sodium form, as shown in Table VI, since both forms are water-soluble.

Following the above procedure, using styrene sulfonic acid solutions of varying concentrations, four additional samples are prepared, with the results tabulated in Table VI, which includes a comparative, unmodified control, sample 10F.

TABLE VI.WET GREASE RECOVERY OF STYRENE SULFONIC ACID MODIFIED POLYAMIDE Acid SO3H Wet Crease Recovery Sample Grafted, Groups Wt. Perper 1O cent gm. Na Form Ca Form 15 540 84 79 18 640 85 25 890 97 100 27 960 97 I00 10E 34 l, 210 97 (ii 101? (Control) 0 none 67 67 The process described herein may also be carried out with highly beneficial results using filamentary structures prepared from other graft copolymer substrates. For example, such structures may be prepared from carbonaceous polymeric textiles to which hydrophilic carbonaceous side chains bearing amide groups are grafted. Thus 66 nylon upon which N-vinyl pyrrolidone or acrylamide is grafted as side chains is suitable. Although these structures are not reset by the ion exchange steps described hereinabove, they are set in a predetermined configuration by Wetting out the said textile structure in the desired predetermined configuration with water (or steam) at a temperature from about 100 C. to that temperature at which substantial hydrolytic degradation of the polymer occurs, and thereafter drying or cooling while in the said desired configuration. In this case, higher temperatures are required to carry out the setting, since the only force available to disrupt and open the fiber structure is that of hydration, not supplemented by ionic forces. The hydroset structure may be temporarily set in a new configuration using dry heat (e.g., 100 to C.), but the original configuration may be re-established by a simple boil-off while the structure is free to retract. The structure may be re-set in a new configuration by repeating the initial setting conditions. In analogous manner, stretch and crepe yarns may be prepared. Moreover, the fibers are rapidly and deeply dyeable, for example, with dispersed dyes.

The principle described above may be applied to preparing settable structures from a wide variety of hydrophobic filament-forming polymers. This may be accomplished by incorporating suificient hydrophilic or water-soluble polymer in the hydrophobic polymer, by grafting or polymer blending, and subjecting the copolymer filaments to a sufficiently severe (in time and temperature) hydrosetting treatment to hydrate the hydrophilic polymer chains, altering the molecular structure of the filament in some manner, which can be deduced, for example, from observation of increased depth and rate of dyeing with disperse dyes. It is an interesting and unexplained observation that hydrosetting achieved by an ionic reaction, as shown in the previous examples, is accompanied by an increase in number and/or size of voids in nylon filaments, whereas hydrosetting without a salt-forming reaction (i.e., using amide modifiers) is accompanied by a decrease in void size. In both embodiments, however, improved wet crease recovery is observed.

This latter embodiment is shown in some of the following examples.

Example 11 A nylon fabric swatch is soaked in 24% aqueous N- vinyl pyrrolidone for hours at room temperature, followed by irradiation of 1 mrad. with 2 mev. electrons. After irradiation, excess monomer and ungrafted homepolymer are removed by rinsin in hot (80 C.) distilled water; the fabric (along with untreated control 11A) is boiled for 30 minutes at 120 C. in a pressure cooker, While held fiat between two screens. After drying a weight gain of 42% is observed, and sample 11B is found to be hydroset in the flat configuration. The wet crease recovery of 118 is 91%, compared to 68% for the control, 11A. Sample 11B is rapidly dyed to a deep black, using a dyebath containing 10% Cibalan Black BGL, a metallized azo dye. Control 11A dyed more slowly to a light shade.

Example 12 A portion of 66 nylon taffeta fabric (7 x 9 inches) prepared from 70 denier 34 filament nylon yarn is placed in a one-gallon polyethylene bag with 30 ml. of N-vinylpyrrolidone, 30 grams of purified sodium styrene sulfomate, and 120 ml. of 15% aqueous sodium sulfate solution. The air bubbles are removed as completely as possible and the polyethylene bag is sealed. The bag is then heated in a water bath at 60 C. for 15 minutes and irradiated for a dose of 1 mrep. at that temperature. The unit rnrep. represents one million rep. (roentgen equivalents physical), a rep. being the amount of high energy particle radiation which results in an energy absorption of 83.8 ergs per gram of water or equivalent. The samples are allowed to remain in contact with the solution for /2 hour before removing from the bag. Thereafter the sample is washed 4 times in distilled water at 80 C. and a weight gain of 28.1% is observed. A portion of this fabric is boiled in 0.5% sodium carbonate solution; another portion of the sample is boiled in 1% calcium acetate solution. The sodium and calcium treated samples are found to have a wet crease recovery of 100% and 90% respectively. Sulfur analyses on the fabrics indicate that about 15% of sodium styrene sulfonate is grafted, and about 10% of N-vinylpyrrolidone.

Example 13 Nylon taffeta samples 6" X 6" square are padded with a solution (as indicated in Table VII), wrapped in aluminum foil and irradiated with 2 mev. electrons, to the indicated dose. Following the irradiation, excess monomer and non-grafted homopolymer are removed by a Tide wash. The observed weight gain is shown in Table VII. The detergent Tide is a product of Procter and Gamble Company of Cincinnati, Ohio. This detergent contains, in addition to the active ingredient, well over 50% 12 (sodium) phosphates (Chemical Industries, 60, 942, July 1947). Analysis shows the composition to be substantially as follows:

Percent Sodium lauryl sulfate 16 Alkyl alcohol sulfate 6 Sodium polyphosphate 30 Sodium pyrophosphate 17 Sodium silicates and sodium sulfate 31 TABLE VII.SAMILE PREPARATION Dose, Wt. Gain, Sample No. Treating Monomer mrep. Percent 13A (Control)... none 40 none 133 100 ml. 50% sq. N-methyl, N-

vinyl formamide. 40 33 13C 100 ml. 100% N-methyl, N-vinyl 40 49 tormamide.

The samples are then tested for wet crease recovery and dyeability, with the results shown in Table VIII.

TABLE VIII.-SAMPLE TESTING Dyeability Sample No. Wet Crease Recovery Rate Washlastness p001 fair fair. fair excellent excellent.

excellent do Do.

Example 14 Graft copolymer yarns are prepared as follows:

Sample 1 4A .-Skeins of denier, 26 filament 66 nylon are soaked overnight in a 20% aqueous acrylamide solution. The excess solution is drained, and the skeins are irradiated while still wet, wrapped in aluminum foil, for one mrad. under the electron beam of the 2 mev. Van de Graaff accelerator. The skeins are thoroughly rinsed and dried.

Sample 14B.l5 lbs. of 80 mesh, 66 nlyon flake are soaked with stirring for 20 hrs. in a solution of 5 lbs. of N-methyl-N-vinylformamide in 9 liters of distilled water. The slurry is irradiated in stainless steel trays, each containing l5002000 ml., for 1 mrad. under a 2 mev. Van de Graaff electron beam. Four liters of water are added to insure agitation and the irradiated flake is allowed to stand in contact with the solution for 2 hrs. The solution is filtered, washed twice for 15 minutes each with three times its volume of water at 20 C., and given a 4 hr. continuous extraction with water at C. The flake is dried for 48 hrs. at 65 C. under vacuum. The fmal 24 hrs. of this period was in a Patterson dryer with tumbling.

The dried flake is spun and drawn using conventional nylon procedures, to a 40 denier, 13 filament yarn.

62,000 yards of the 40 denier yarn are plied to give 31,000 yards of 80 denier, 26 filament. 8,000 yards of the 80-26 yarn are twisted to /2 Z, wound on 3 spring bobbins, and hydroset in a preboarding oven at 26 psi. steam for 2 hr 8,000 yards of 8026 /2S yarn is prepared in the same manner.

Sample 14C.-Eighty mesh 0.3% TiO 66 nylon flake is soaked overnight in 10% aqueous N-vinylpyrrolidone (3/1 bathzpolymer ratio). The slurry is irradiated in shallow pans containing a layer 1 cm. or less under the electron beam of the 2 mev. Van de Graaff accelerator for one mrad. after which the flake is drained, thoroughly rinsed with distilled water, and dried. A nominal 10% modification is obtained. The flake was melt-spun and cold drawn as for 1413.

The yarns are hydroset by first treating the untwisted yarn with superheated steam in a preboarding oven at 'pared from polymer blends.

130 C. (26 psi) for 2 hours. They are then twisted to 55 turns per inch, one-half of the yarn being twisted to 55S and the other half to 552; the twist is stabilized for weaving by heating the yarn in dry heat at 100 C. for 2 hours.

This yarn is woven as filling yarn (7089 denier) into a stock nylon warp (70 denier) in a standard crepe construction (plain weave with 2 picks of S yarn alternating with 2 picks of Z yarn). The fabrics are scoured (to allow creping) by immersing them in an olive oil-soap bath at room temperature, bringing the bath to the boil over a -rninute period and boiling for 30 minutes. When the fabric is rinsedand dried, the final fabric width is measured and the uniformity of the creping is determined subjectively. The fabric shrinkage, crepeability and crepe uniformity are listed in the table.

TABLE LX.-POLYMER MODIFICATIONS TESTED FOR HYDROSEITING The crepes are finally stabilized by heat setting on a tenter frame at 220 C.

The crepe produced is much more uniform than that obtained using an unmodified nylon control.

Example A taffeta fabric made from 70 denier 34 filament linear polypropylene is soaked for 30 minutes at 60 C. in a sealed polyethylene terephthalate bag in g. distilled N-vinyl-pyrrolidone with 10 g. methanol and 70 g. cyclohexane. The bag and contents are then irradiated hot with 3 mev. electrons for 2.4 mrad. After a hold-up time of 30 minutes the fabric is thoroughly scoured at 50 C., dried and Weighed. The weight gain is 39.5%.

The hydrosettable characteristic of this fabric is shown by the following experiment.

A strip of fabric 2" wide is creased under a 5 lb. weight and steam set in a pressure cooker for 15 minutes at 120 C. The so-formed crease is removed by dry ironing, but returns upon wetting with water.

Example 16 Filamentary structures suitable for hydrosetting according to the process of the instant invention may be pre- Process conditions and a wide variety of components for forming these polymer blends are described by E. E. Magat in U.S. application Serial No. 8,586, now abandoned, as exemplified below.

An aqueous solution of hexamethylene diammonium adipate (66 nylon salt) is charged to an autoclave and polymerized following conventional procedures. During the process, when the degree of polymerization has reached a value of from 1 to about 10, an aqueous solution of polyvinyl pyrrolidone is injected into the pressurized auto- The flake is dried, charged to a screw melter and extruded through a 34-hole spinneret to form yarn, which is thereafter drawn to a draw ratio of 4X; the final denier is 70. The yarn is woven into a nylon taffeta. The yarn is woven to a plain weave 76 picks, 120 end taffeta fabric. A swatch of this fabric is creased, and then steamed at 26 lbs/inch for 2 hours after which the fabric is dried and is ironed flat at 140 C. The crease disappears. The fabric is then soaked in water while it is free to recover; a crease recovery of 98.1% is observed. When an unmodified nylon control fabric of similar construction is tested in this way, the crease recovery is only 83.8%.

Example 17 A polyamide is prepared by melt polymerization of paraxyly-lene diamine and azelaic acid. The conventionally prepared polymer is extruded to filaments which are then drawn and woven to form a fabric. A swatch of the fabric is soaked for 24 hours at 60 C. in 20% aqueous N-vinyl pyrrolidone. Excess liquid is squeezed from the fabric, which is then placed in a polyethylene bag and irradiated with 2 mev. electrons to a dose of 1 mrad. After rinsing and drying, the weight gain is found to be 9%. The fabric is then tested according to the procedure of Example 15, to demonstrate the ability of the fiber to produce an acceptable crepe. The grafted polyamide shows a recovery of A control, which is not modified, shows a recovery of 77%.

When tested according to the above procedure, a fabric from 6 nylon (polymer prepared by polymerization of caprolactam) grafted with 8% polyvinyl pyrrolidone shows a recovery of nearly 100%.

Example 18 'Fabric prepared from Verel (an acrylonitrile-vinylidene chloride copolymer) staple filaments is soaked for 30 minutes in 20% acrylic acid at C., and irradiated (at 90 C., while still wet) with 2 mev. electrons to a dose of 1 mrep. Excess acid and ungrafted homopolymer is removed by soaking in water at 80 C. The acid-grafted fabric (weight gain, 14.8%) is converted to the sodium salt and simultaneously set by boiling in 1% aqueous Na Co while the fabric is held fiat between two pieces of screen. After rinsing'and drying, the wet crease re covery is found to be as compared to 52% for an unmodified control.

Example 19 A swatch of wool fabric is soaked for 30 minutes in 25% aqueous acrylic acid, then irradiated with 2 mev. electrons while wet, using a dose of 1 mrad. After rinsing in hot water, the weight gain is found to be 11% The acid-grafted fabric is hydroset between screens while it is converted to the sodium salt by heating (60-80 C.) for 1 hour in 2% aqueous Na CO When the wet fabric is sharply creased by pressure (at room temperature), the crease disappears almost immediately when the pressure is removed.

When the test is repeated with swatches of sodium acrylate-grafted rayon and silk, similar results are obtained.

WET CREASE RECOVERY The improved Wet crease recovery obtained as a result of the process of this invention is surprising, since all conventional fibers show either poorer or, atbest, constant crease recovery as the relative humidity is increased. This property is recognized in that conventional fabrics, wrinkled in use, are wetted and then ironed to dryness to remove wrinkles. In contrast, fabrics set according to the process of this invention show improved crease recovery as the relative humidity is increased (as shown in the following table), so that wrinkles'may be removed by merely wetting the set fabrics and hanging up to dry, without need for ironing.

TABLE X.OREASE RECOVERY VS. RELATIVE HUMID T 1 Relative humidity. 2 Set in the flat condition, as described hereinabove.

Example 20 Fabric is prepared from conventionally drawn (5.6 draw ratio) polyacrylonitrile copolymer yarn, the copolymer composition being 93.5 parts (by weight) acrylo nitrile, 6 parts methylacrylate, and 0.5 part sodium styrene sulfonate. The fabric is soaked in 20% aqueous acrylic acid at a temperature of 90-95 C. for 60 minutes, and is irradiated using the 2 mev. electron accelerator, to a dose of 1 mrad. Following a standard wash and a rinse in boiling water, the Weight gain of the sample is After treating the acrylic acid-modified test fabric in a flat configuration with 0.5% aqueous sodium carbonate at the boil, the fabric shows a 73% wet crease recovery at 50 C., as compared to 35% for a control fabric. When an attempt is made to repeat the test using a fabric prepared from conventional random copolymer filaments having the same final chemical composition (i.e., containing the 10% additional acrylic acid) as the grafted sample, the fabric disintegrates in the boiling sodium carbonate solution.

When methacrylic acid is used in place of acrylic acid, similar results are obtained.

Although the preferred method of carrying out the process of this invention is to treat a graft copolymer bearing hydrophilic grafts with water, the same principle can be employed using a hydrophobic graft, setting with a solvent which would swell (or dissolve) the grafted component as a homopolymer, as shown by the following example.

Example 21 A swatch of 66 nylon fabric is soaked overnight in a solution of 90 parts styrene and 10 pmts phenol. Excess liquid is squeezed from the fabric, which is then irradiated with 2 mev. electrons at -80 C. to a dose of 3 mrad. The fabric is allowed to warm to room temperature overnight, and ungrafted homopolymer removed and the fabric is simultaneously set fiat by successively rinsing in hot toluene and benzene. The dry fabric has a weight gain of When the dry fabric is crumpled in the hand, then immersed in benzene, the wrinkles are immediately removed.

POLYMER SUBSTRATES Although any linear, fiber-forming or fibrous carbonaceous polymer may serve as the substrate which, when modified as described hereinabove, may be used in the process of the instant invention, the preferred substrates are the synthetic linear fiber-forming polyamides which are characterized by recurring amide linkages as an integral part of the polymer chain.

Although homopolyamides will normally be preferred as a substrate for preparing the textile of the instant invention, copolyarnides may also be employed, as well as mixtures of polyamides. The preferred polyamides are those which have a low or intermediate value for the second order or glass transition temperature (T The second order transition temperature is that temperature at which there is a change in slope in the curve relating certain polymer properties (e.g., volume) to temperature. The preferred method of making this determination is 16 described in detail by H. A. Stuart in Die Physik der Hochpolyrnere, vol. 4B, pp. 48-97, Springer Verlaek, West Germany (1956). In this test, the dynamic modulus of the fiber is determined as a function of temperature. The fiber is tested dry, at 0.01 cycle/sec, before grafting.

Suitable polyamides for preparing the dyeable crosslinked textile of this invention are those synthetic linear polyamides which are prepared from polymerizable monoamino monocarboxylic acids or their amide-forming derivatives, or from suitable diamine and suitable dicarboxylic acids or from amide-forming derivatives of these compounds. The preferred polyamides are those wherein the intracarbonarnide linkages are other than exclusively aromatic, i.e., there is at least 1 aliphatic group in each repeating unit of the polymer molecule wherein R-- is a member of the class consisting of hydrogen, halogen, monovalent organic radical, alkylene or the like. Typical of such polyamides are those formed from an aliphatic diamine and an aliphatic acid and containing the repeating unit --X--Z-Y-Z-- wherein X and -Y represent divalent aliphatic or cycloaliphatic groups and -Z represents the linkage. Polyhexamethylene adipamide, polycaproamide and polyundecanoarnide (i.e., 66, 6 and 11 nylons) are typical. Additionally polyamides having repeating units such as wherein B-- is divalent alkaryl (such as xylylene) may be used. Preparation of the high molecular weight polyamides is illustrated in US. Patents Nos. 2,071,250, 2,071,253, and 2,130,948.

The preferred polyamides for producing the crepeable textile of the instant invention are those which have a medium to low value of T These polyamides are preferred because high T polyamides usually show such high crease recovery that little improvement in crease recovery is obtainable. Those polyamides with a low value for T,;, e.g., in the neighborhood of C. and below, are usually readily hydroset and show ready crepeability as a result. The T g varies somewhat depending on method of measurement, but polyamides typical of each group are listed below.

Typical high T,, polyamides are those obtained by polymerizing metaphenylene diamine and isophthalic acid, bis(para-aminocyclohexyl)methane and sebacic acid, hexamethylene diamine and isophthalic acid, dimethyl-metaphenylene diamine and seb'acic acid. These polyamides have a T of C. and above. In contrast, the most adaptable substrates for the present invention are such polyamides as hexamethylene adiparnide, polyundecanoamide, polyamide from meta-xylylene diamine and adipic acid, the polyamide from para-Xyiylene diamine and azelaic acid, polycaproamide, and poly(hexamethylene adipamide/sebacamide) copolymer (50/50, mol percent), which have T values ranging from 50 C. to 125 C.

STRUCTURE CHANGES PRODUCED The novel results obtained by the process of the present invention are believed to be caused by a change in the fiber structure. While applicants do not wish to be bound by any theory, the effects produced when a saltforming reaction accompanies setting may be better understood in terms of the following structural explanation, using acrylic acid grafted 66 nylon as an illustration.

It is believed t at the acid-grafted nylon consists of a grafted to the polyamide chains throughout the fiber and extending out along the fiber surface. At this stage, no observable structural changes are noted except for an increase in fiber denier commensurate with the amount of grafted polyacrylic acid. The original dimensions of the fiber remain essentially unchanged as does the wet crease recovery and most other physical properties.

When the acid-grafted nylon reacts with sodium ions at room temperature, the fiber becomes highly hydrophilic because of the water-solubility of sodium polyacrylate. There is some hint that the fiber is now under strain while immersed in water, and there are some forces operating which are in favor of a more preferred structure. For example, a fabric thus treated begins to shrink and exhibit some improvement in wet crease recovery if it is allowed to stand in water at room temperature for several days. It is believed that the grafted chains of polyacrylic acid, which are now present as sodium polyacrylate salt, are essentially anionic polyelectrolytes; ionic forces are involved and electric charges of the ionized COO radicals mutually repel each other. In addition, hydration undoubtedly occurs, further distending the chains. As a result of these forces, the grafted polymer chains attempt to uncoil. When the water temperature is increased to about 60 C. or preferably up to 100 C., the fiber structure is somewhat relaxed and plasticized, thereby allowing the coiled chains to uncoil and extend themselves. In so doing, the fiber swells, which leads to the observed increase in cross-sectional area and the shrinkage of the yarn. In the process of uncoiling under the impetus of heat and water the extended polymer grafts also intermingle with each other to a much higher extent than before. This occurs on the surface as well as throughout the fiber and in so doing configuration restrictions are imposed on the fabric. This structure is that produced by the hydrosetting process, It is characterized by high wet crease recovery, resistance to the formation of wrinkles, and it is more dyeable than untreated and unmodified nylon.

In the dry state, the sodium polyacrylate chains remain intermingled but are deflated and no not greatly influence crease recovery or wrinkle resistance since the grafted chains are no longer swollen or rigid.

When hydroset sodium acrylate-grafted nylon is converted to the acid form by regeneration in a dilute acid solution, the grafted polymer is no longer a poly-anion I and the accordion-like chains return to their more coiled configuration. Thus, the acid form is not effectively set I by water at the moderate temperatures which are not satisfactory with the sodium salt form. However, the open structure created in the original setting of the sodium salt remains, so that the fiber retains its deep dyeability. Thus, as described above, new creases permanent to ironing or boil-01f can be formed or removed reversibly by going back and forth between the Na and -H forms.

The usual way of reforming (i.e., rehydrosetting) the hydroset structure, especially when ion exchange is not possible, is by hot-wet ironing or steaming. For example, if a fabric which has been hydroset in the fiat position is wetted with water and folded, and the crease ironed to dryness at about 45 C. (preferably 60 C. or above), the fabric will now be re-hydroset in the creased configuration. Thus, if the re-hydroset crease is ironed out with a dry hot iron, it will immediately reappear when the fabric is dipped in cold water. It is believed that this re-hydrosetting occurs under mechanical deformation combined with hot-wet treatment followed by drying or cooling, because .the moisture is being squeezed from the ..,fiber, and .the coiled side chain grafts are being dehydrated and forced into the new creased configuration. This process is facilitated by moist heat, which softens the ,Substrate backbone and along with the pressure, collapses the original canals formed during the first hydroset process, and forms new ones which constitute the re-hydroset l3 form. Hot-Wet treatment alone does not complete the hydrosetting step. Cooling or drying out at the site of hydrosetting is required, if the configuration is to become permanent.

As indicated above, the high wet crease recovery properties of hydroset sodium acrylate grafted nylon is not unique to the sodium salt, since other monovalent cations such as potassium, lithium or ammonium also confer these attributes. As noted in the examples, the insoluble calcium polyacrylate salt derivative cannot be hydroset under the same moderate conditions. This is believed due to the limited ionization of the insoluble calcium polyacrylate salt.

The structure changes described above have been followed by means of high and low angle X-ray techniques for samples soaked overnight in 30% acrylic acid and subsequently irradiation grafted. The results of this study show that the amount of dififuse low angle X-rayscattering increases on conversion of the acrylic acid-grafted nylon to the sodium salt form, and the observed distribution of apparent void content shifts to larger size voids. This structural change appears to be permanent since the apparent void size distribution is relatively unchanged when the sodium form is reconverted to the H form. Thus, this observation correlates with the known changes in physical property such as increased wickability and dye ability. Conversion to the calcium acrylate form directly from the hydrogen form opens the structure less than conversion to the sodium form. However, when the calcium acrylate form is regenerated from the sodium form, the highly opened structure is retained, although the improved wet crease recovery is lost.

The structure changes observed on hydrosetting not involving salt-formation are somewhat difierent, as previously indicated, although similar results (e.g., improved we crease recovery) are obtained. The substrates showing this latter behavior may be exemplified by polyamide with grafted N-vinyl amide, or polyamide blended with poly(N-vinyl amide), In this case, hydrosetting produces extensive recrystallization, which is probably related to the hydrophilic nature of the modifier. 'This structure change has been observed using X-ray dilfraction techniques; a significant increase in average lateral crystal dimension, D010, This increase is at least about 25% over that of non-hydroset filaments. For 66 nylon vwith grafted N-vinyl pyrrolidone or melt-blended polyvinyl pyrrolidone, the absolute lateral crystal dimension after hydrosetting (D will be above 35 Angstrom units. The higher degrees of modification show larger changes and correspondingly greater effects. For example, 66 nylon fabric with 30% N-vinyl pyrrolidone grafted thereto (according to the technique of Example 11), shows an increase of 70% in average lateral crystal dimension on hydrosetting for two hours in 15 p-.s.i.g. steam. These structural changes describe the product produced when the process of the instant invention is applied to polyamide substrates with grafted vinyl amide or blended polyvinyl amide.

CRYSTAL SIZE DETERMINATION The average lateral crystal dimension is determined from the X-ray line broadening of the principal outer equatorial diffraction maximum. This maximum is given by the 010 and diffraction planes which have a Bragg spacing of about 3.7 A in the 66 nylon crystal (C W. Bunn and E. V. Garner, Proc. Royal 500., 189A, 39 1947]. The average size is calculated by using Warrens correction for Scherrers line broadening equation (realizing the assumptions inherent in the derivation (H. P. King and L. F. Alexander, X-ray Diffraction Procedures, John Wiley and Sons, Inc., New York, 1954, chapter 9) B"=,8 +b where fl=pure breadth of a diffrac tion having wavelength x and Bragg angle 0, Bexperimentally observed breadth, and b=breadth due to instrumental conditions. Then where D=mean dimension of the crystallites in Angstroms and K constant. In the present work the dimension is defined as the effective thickness of a crystallite perpendicular to the diffracting planes, and is designated D010, Line breadths are measured at half-maximum peak intensity, and accordingly the value of K is taken to be 0.9. In reducing the data a suitable background correction is made. Since there is some overlapping of the two principal equatorial diffraction maxima, the experi mentally observed breadth, B, is determined by bisecting the outer maximum at the point of peak intensity and doubling the half-maximum intensity breadth measured on the high angle side. This is equivalent to assuming that the inner maximum does not influence the intensity distribution on the high angle side of outer maximum.

PROCESSING CONDITIONS Drying the acid-grafted textile after any prior wetting with a solution containing the appropriate positive ions at room temperature is sufficient to cause some setting of the structure. If the exposure is at room temperature however, noticeable effects require wetting out for a relatively long period, e.g., 48 hours. To attain a practical rate, contacting temperatures of 60 C. or higher are recommended. As pointed out hereinabove, the sodium salt may be formed before but is preferably formed at the same time as the wetting out at elevated temperature. It will usually be satisfactory to carry out the wetting out at 100 C. although higher temperatures may be employed in order to achieve shorter contact time. Exposures of 5 minutes at 180 C. or 2 minutes at 220 C.

may be employed with sodium acrylate grafted nylon. Usually, temperatures high enough to cause substantial degradation of the fiber are to be avoided.

The desired predetermined configuration is impressed upon the textile before or during the treatment of wetting out at elevated temperatures. It is usually desirable to mechanically restrain the filamentary structure in the predetermined configuration during the setting operation (e.g., via twisting, use of a tenter, or pressing while drying or cooling), but good results are obtained when tension or pressure is not practical during drying or cooling, for example, when drying relaxed but crimped staple.

It is desirable to cool the textile structures while in the predetermined geometric configuration or, alternatively to bleed off the steam or treating solution, which helps in retaining the preferred shape during drying.

GMFT COPOLYMERS Any textile formed from a carbonaceous polymer by nature or by man and bearing grafted side chains of markedly different solubility from the substrate polymer is suitable in the process of the present invention. It is preferred that the grafted side chains be present in polymeric form since these chains can better exert the necessary force required to distort the fiber structure, and simultaneously retain the set configuration against external pressures. Conventional mixtures of pro-formed polymers are also satisfactory, but it is preferred that they be prepared by melt-blending, whenever possible, since otherwise, the water-soluble component may be lost in laundering, unless chemical attachment of the two pre-formed polymers is attained, for example by high energy irradiation grafting.

The vinyl modifiers useful in forming the grafted sidechains include those monomers whose polymers in the non-grafted form are soluble in a liquid which is not a solvent for the grafted structure. Such compounds which form water-soluble ionic salts (from either positive or negative ions) are particularly useful. Thus unsaturated monoacids are suitable, such as for example acrylic, methacrylic, ethylacrylic, crotonic, propiolic, and styrene carboxylic acids. Suitable acids should be homopolymeriz able, but may be copolymerizable if the comonomer combination forms long chains in the grafting reaction. If desired, other derivatives may be employed such as acid chlorides, acid anhydrides, half acid esters, and half acid amides; these may be subsequently converted to the acid form. Indeed, any organic compound with aliphatic unsaturation, containing functional groups which are con vertible to the acid form by hydrolysis (e.g., amides, esters, nitriles), oxidation (aldehydes or ketones) or the like is suitable.

In addition to the unsaturated carboxylic acids, other acids are useful. Such acids are the unsaturated sulfonic acids, unsaturated alkyl or aralkyl acid phosphates, phosphites, phosphonates and phosphinates; acid alkyl sulfates and carbonates with unsaturated carbon-carbon bonds also have utility. As an example of the sulfonic acid class, styrene sulfonic acid is especially useful, as shown hereinabove. Other salt-forming monomers may be em ployed to form the graft copolymer suited for the instant invention. Thus, such amines as pyridine, allylamine, vinylamine and the like may be employed, provided they are of sufficiently low molecular weight to penetrate into the polymer before grafting is induced. As disclosed previously, a pre-formed salt-forming polymer may be blended with the substrate polymer; they may be later bonded together by chemical linkages.

The preferred non-salt-forming modifiers for grafting to the polymer substrate are the N-vinyl amides such as N-alkyl, N-vinyl formamides (e.g., N-methyl, N-vinyl formamide) and especially N-vinyl lactams such as N-vinyl pyrrolidone. Poly(N-vinyl pyrrolidone) is especially preferred for melt-blending with polyamides.

AMOUNT OF MODIFIER The amount of modifier required to obtain a readily hydrosettable textile will vary widely. In the case of the sodium acrylate derivative at least about 250 equivalents of salt-forming polymer per 10 grams of polymer is grafted to the polymer substrate, and preferably at least 500800 such groups, The maximum concentration of such groups will usually be limited to an amount which avoids making the graft copolymer soluble in water. Satisfactory results are readily obtained at much lower values. As a guide, from 1000 to 4000 equivalents of carboxyl groups per 10 grams of polymer are satisfac tory when the substrate is a nitrogenous condensation polymer. The concentration of acid groups is determined by titration or by a calculation based on weight gain.

For the non-salt-forming modifier, at least 5% and preferably 7%, based on substrate weight, should be employed. Larger amounts are often more effective, good results being obtained with 4-0 to 50% or more.

The importance of having the graft copolymer modification extend throughout the bulk of the filaments to be treated by the process of this invention has already been mentioned. It is preferred that the grafting reaction be initiated under such circumstances that excess modifier is present on the surface of the filaments, so that there is a certain amount of surface modification in addition to that achieved throughout the bulk of the filament. This is attained, for example, by irradiating the filaments while they are soaking wet with modifier. This appears to enhance response to the setting procedure, although useful results are obtained when the surface modification is absent, e.g., for filaments prepared via melt blending.

Temporary setting to conceal the prior hydroset is conveniently accomplished by tension or a dry heat treatment,. as disclosed hereinabove. Suitable temperatures range from 130 0., preferably not exceeding C. After the temporary setting has been attained, it is important to keep the treated filamentary substrate dry to retain the effect of the temporary setting until subsequent at processing steps have been carried out. When these steps have been completed it is then merely necessary to wet the filamentary structure with water in order to return to the -hydroset configuration. Although aqueous treatment at room temperature is satisfactory, results will be .obtained more quickly and to a greater degree if the treatment occurs at elevated temperature while the structure is free from restraint.

U'I ILITY The advantages of the process of the present invention are immediately apparent. It provides a process for imparting a permanent set to textiles whereby the need for high temperature ovens, autoclaves and the like is largely avoided. Instead, the setting process can be carried out by a simple ionic treatment that does not require the use of high temperatures. Such treatments may be readily combined with conventional textile processing (e.g., dyeing, scouring, bleaching), as shown in the examples.

The examples show that the process of the instant invention is useful in making a continuous filament crepe yarn, or a stretch yarn.

The crepe fabrics produced by the process of this invention, using modified polyamide substrates, are different from the crepes customarily accepted in the trade. These traditional crepes are made from the viscose or acetate rayon. These traditional crepes cannot be washed because they are not dimensionally stable. The slightest drop of water will ruin a dress made of these fabrics. In contrast, the crepes made from polyamides according to the process of this invention are truly wash-wear fabrics and may be hand washed and are ready to Wear with a minimum of ironing.

Attempts to make crepes from prior art unmodified fibers, such as ordinary 66 nylon, were generally unsuccessful, even though a much higher degree of twist was used in order to obtain proper crepeing forces. This twist makes the yarn so lively that it is almost impossible to weave. Attempts to subdue the twist liveliness by the use of conventional sizes have been generally unsatisfactory because of cost, difliculty in removing the size completely, and the fact that even under these conditions, the twist is not sufficiently stabilized. The hydroset polyamide yarns of this invention are, however, readily stabilized by a dry heat treatment, and may be woven to produce highly acceptable wash-Wear crepe fabrics.

In addition to the above, crimped staple filaments may be set to form a product of high crimp and crimp re tention. The process of the present invention is useful in the waving or straightening of human hair. The structure may also be used in alarm devices and in automatic controls devices where water sensitivity is required. Hydroset structures permit easy wrinkle removal during dry cleaning.

The hydroset product of this invention is more easily reset to a new configuration than are unmodified prior art textiles, even though the initial hydrosetting produces a much more effective initial set. Thus nylon taffeta with 8.2% N-vinyl pyrrolidone graft, hydroset three times in succession, as follows: (1) fiat; (2) creased; and (3) flat, in an average of 5 tests each, produces a crease angle of 159 (88.5% recovery) whereas a control of similarly treated unmodified 66 nylon has a recovery of only 145 (80.5%).

In addition to the above-mentioned advantages, the process of the instant invention also impaits an open structure to the filaments so that they are especially suitable for dyeing (increased rate and depth), and they respond to resin treatments of various sorts. These filaments are especially for all applications where a porous structure is advantageous.

Although the process of the instant invention has been described as a batch operation, it is obvious that it may be readily adapted to continuous operation. Thus, acidgrafted nylon may be continually immersed in a sodium be dipped in the appropriate ion treating solution, and

then passed through an oven or through a mangle or other ironing device whereby the fabric is set in the desired configuration.

Many obvious modifications of the above will be apparent to those skilled in the art from a reading of the present disclosure without a departure from the inventive concept.

This application is a continuation-in-part of United States application 784,075, filed December 31, 1958, and now abandoned.

What is claimed is:

1. In the production of textile structures that are processed in a configuration different from the desired final configuration, the improvement for introducing a predetermined stable con-figuration that can be altered temporarily for processing and then be restored by relaxing the structure which comprises preparing a textile structure of a polymer having hydrophilic side chains, wetting out the structure in a predetermined configuration and drying the structure to hydroset the configuration, the hydroset being introduced at a temperature of at least 60 C. and below that at which significant degradation of the polymer occurs, resetting the hydroset structure in a different configuration with dry heat at temperatures imparting a temporary configuration, and subsequently wetting out the structure in a relaxed condition to remove the temporary configuration and restore the hydroset, said polymer of the structure being selected from the class consisting of (a) a polymer of a substrate of a carbonaceous polymeric textile modified, substantially throughout its cross-sectional area, with graft-polymerized side chains derived from an addition-polymerizable monomer selected from the class consisting of an unsaturated organic acid, a water-soluble salt thereof, an unsaturated organic amide, an unsaturated amine, and an unsaturated alcohol, the said side chains in the homopolymerized non-grafted form being soluble, or at least highly swellable, in water, and (b) a polymer mixture of a synthetic linear fiber-forming polymer and a compatible watersoluble polymer obtained by addition polymerization of an unsaturated monomer of (a above.

2. A process as defined in claim 1 wherein the hydrophilic side chains of said polymer are water-soluble salts of a graft-polymerized unsaturated acid.

3. A process as defined in claim 2 wherein said polymer is in the form of the sodium salt when the structure is hydroset.

4. A process as defined in claim 1 wherein said structure is hydroset by pressing the desired configuration in the wet structure until the structure is dry.

5. A process as defined in claim 1 wherein said hydroset structure is reset by dry pressing at to C. to impart said temporary configuration.

6. A process as defined in claim 1 wherein said hydroset structure is a yarn and is reset under tension to impart said temporary configuration.

7. A process as defined in claim 1 wherein said textile structure is a multifilament yarn, the filaments are hydroset in one twist configuration and then reset with dry heat in a different configuration, a fabric is prepared from the reset yarn and the fabric is thereafter wet out in a relaxed condition to restore the hydroset in the filaments.

References Cited in the file of this patent UNITED STATES PATENTS 2,144,677 Dreyfus et a1. Jan. 24, 1939 2,290,253 Schneider July 21, 1942 2,369,395 Heyman-n Feb. 13, 1945 (Other references on following page) 23 UNITED STATES PATENTS 2,686,955 2,837,496 Remhardt et a1. May 30, 1950 2 857 653 Van Heck Oct. 3, 1950 2:999:0S6 Foster Nov. 6, 1951 5 Hemmi Dec. 30, 1952 Stanley et1a1 May 26, 1953 679,562

24 Luther Aug. 24, 1954 Vandenberg June 3, 1958 Ephland Oct. 28, 1958 Tanner Sept. 5, 1961 FOREIGN PATENTS Great Britain Sept. 17, 1952 

1. IN THE PRODUCTION OF TEXTILE STRUCTURES THAT ARE PROCESSED IN A CONFIGURATION DIFFERENT FROM THE DESIRED FINAL CONFIGURATION, THE IMPROVEMENT FOR INTRODUCING A PREDETERMINED STABLE DONFIGURATION THAT CAN BE ALTERED TEMPORARILY FOR PROCESSING AND THEN BE REESTORED BY RELAXING THE STRUCTURE WHICH COMPRISES PREPARING A TEXTILE STRUCTURE OF A POLYMER HAVING HYDROPHILIC SIDE CHAINS, WETTING OUT THE STRUCTURE IN A PREDETERMINED CONFIGURATION AND DRYING THE STRUCTURE TO HYDROSET THE CONFIGURATION, THE HYDROSET BEING INTRODUCED AT A TEMPERATURE OF AT LEAST 60*C. AND BELOW THAT AT WHICH SIGNIFICANT DEGRADATION OF THE POLYMER OCCURS, RESETTING THE HYDROSET STRUCTURE IN A DIFFERENT CONFIGURATION WITH DRY HEAT AT TEMPERATURES IMPARTING A TEMPORARY CONFIGURATION, AND SUBSEQUENTLY WETTING OUT THE STRUCTURE IN A RELAXED CONDITION TO REMOVE THE TEMPORARY CONFIGURATION AND RESTORE THE HYDROSET, SAID POLYMER OF THE STRUCTURE BEING SELECTED FROM THE CLASS CONSISTING OF (A) A POLYMER OF A SUBSTRATE OF A CARBONACEOUS POLYMERIC TEXTILE MODIFIED, SUBSTANTIALLY THROUGHOUT ITS CROSS-SECTIONAL AREA, WITH GRAFT-POLYMERIZED SIDE CHAINS DERIVED FROM AN ADDITION-POLYMERIZABLE MONOMER SELECTED FROM THE CLASS CONSISTING OF AN UNSATURATED ORGANIC ACID, A WATER-SOLUBLE SALT THEREOF, AN UNSATURATED ORGANIC AMIDE, AN UNSATURATED AMINE, AND AN UNSATURATED ALCOHOL, THE SAID SIDE CHAINS IN THE HOMOPOLYMERIZED NON-GRAFTED FORM BEING SOLUBLE, OR AT LEAST HIGHLY SWELLABLE, IN WATER, AND (B) A POLYMER MIXTURE OF A SYNTHETIC LINEAR FIBER FORMING POLYMER AND A COMPATIBLE WATERSOLUBLE POLYMER OBTAINED BY ADDITION POLYMERIZATION OF AN UNSATURATED MONOMER OF (A) ABOVE. 